An industrial estate on the outskirts of a sleepy spa town in deepest Powys, Wales, may not strike you as the obvious place to find an ambitious little hydrogen vehicle maker with plans to revolutionise the way we power, drive, and own our cars. But it shouldn’t come as that much of a surprise that it's there.

Why not? Well, if you drive seventy-five miles to the south-west from Riversimple’s HQ in Llandrindod Wells, you end up in Swansea, once the home of William Robert Grove who in 1842 pretty much invented the hydrogen fuel cell. And it’s a hydrogen fuel cell that part-powers the Rasa, Riversimple’s funky little two-seater prototype.

"Part-powers?" I hear you ask. While the majority of electric and hydrogen cars currently on the market are essentially conventional designs with battery or fuel-cell-and-battery power sources, the Rasa—the name comes from tabula rasa, the Latin for blank or clean slate—is the result of altogether more clever thinking. I’m inclined to use a word I usually avoid like the plague—holistic—to describe Riversimple’s view of automotive design.

The first clue to what’s afoot here is the fuel cell itself. The unit in the Rasa is an off-the-shelf component with a piffling 8.5kW output that's best known for powering forklift trucks in Walmart warehouses. Compare that to the 100kW fuel cell in the Hyundai ix35 Fuel Cell or the 114kW stack in Toyota’s Mirai. Despite that limp output, the prototype Rasa can hit 60mph (which is also its top speed) in under 10 seconds.

Further Reading

The Rasa uses a number of clever techniques to pull off this low-power but decent performance trick. To start with the vehicle has a low drag coefficient of 0.248. I’ve passed wind with more drag than that. Next is its weight: at 580 kilos (1278lbs) all-in, the Rasa is only 130kg heavier than Renault’s Twizy. And that’s as much scooter as car. Lastly but most importantly is the unusually efficient regenerative braking system that harvests the kinetic energy usually wasted under retardation from the four in-wheel traction motors.

The clever part in all this is that the fuel cell only solely powers the Rasa when it is cruising. An average family car uses about twenty percent of the engine's output when wafting along at a steady 70mph. For acceleration or climbing hills, the Rasa summons extra power from four banks of lithium-ion hybrid capacitors that store the energy recuperated from the braking system.

The advantage of super capacitors over batteries is that you can dump a large amount of energy into them quickly without anything going “bang” and without doing long-term damage. The downside is limited storage capacity.

The lithium-ion hybrid capacitors used in the Rasa consist of 120 cells with a capacitance of 3300F each and a total energy storage capacity of 1.9MJ or 0.53kWh. They offer a best-of-both-worlds compromise: only slightly less robust energy capture than a supercapacitor but higher energy storage capacity.

What all this means is that the power sources for cruise and acceleration are decoupled. This is the reason Riversimple calls the Rasa a “network electric car." The electric drive system uses power from varying sources as and when needed.

Body panels can be removed in a trice. Sometimes faster.

Alun Taylor

Finished cars will feature self-coloured body panels.

Alun Taylor

Off-the-shelf fuel cell is also used in Walmart forklift trucks, fact fans.

Alun Taylor

Hydrogen fuel filler is standard across all hydrogen cars.

Alun Taylor

Looks may divide opinion. In my view, this motor has something of a Dan Dare vibe.

Alun Taylor

No boot present in the prototype. Production version, we're promised, will have 170L capacity.

Alun Taylor

Doors down.

Alun Taylor

Doors up.

Alun Taylor

Flat underside helps with super low CoD.

Alun Taylor

Front light cluster close up.

Alun Taylor

Gull wing doors: not the easiest to open, but at least they don't drop on your head.

Alun Taylor

Li-ion hybrid capacitors on test bench.

Alun Taylor

Alun Taylor

Alun Taylor

Alun Taylor

Alun Taylor

Alun Taylor

Rear light cluster detail.

Alun Taylor

Rear three-quarter panel is a supremely fluid piece of design.

Alun Taylor

Rear wheels are covered to reduce drag and look retro cool.

Alun Taylor

Skinny Michelin rubber helps economy.

Alun Taylor

Vents not just for show. Water vapour from the fuel cell exists here, too.

Alun Taylor

Wheel and wheel motor, along with the Lotus Elise strut.

Alun Taylor

Granted the top speed may seem a little on the low side, but it’s worth clarifying that Riversimple envisages the Rasa as a fundamentally local car for running around—not one for long-distance motorway cruising. A higher top speed would necessitate a more powerful fuel cell and that goes against the grain of what Riversimple is trying to achieve.

Most of you reading this will have an idea of how a hydrogen fuel cell works. But for those who don’t: the Hydrogenics fuel cell in the Rasa has two electrodes—a negatively charged anode and a positively charged cathode. The anode is supplied with hydrogen and the cathode with oxygen. The hydrogen molecules are attracted to the cathode through a membrane that is designed to allow only protons (H+) to pass through, not electrons.

The H+ ions pass through the membrane to combine with the oxygen, creating the only byproduct of the process: water. The electrons, meanwhile, are blocked at the anode level and can only move into an external circuit, thus generating an electric current. As a method of power generation it’s roughly twice as efficient as a petrol engine, as well as cleaner, more compact, and more reliable.

Locomotion meanwhile comes courtesy of four radial, flux-wheel, hub-mounted motors developed specially for the Rasa by Printed Motor Works of Alton in Hampshire. The total power output of the drivetrain is 16kW continuous and 55kW peak. Each motor generates 60Nm continuous and 170Nm peak torque.

Thanks to those four motors, the Rasa can recover more than 50 percent of the available kinetic energy when braking. The cunning part of the Rasa’s efficient recuperative braking is due to something Riversimple calls phased braking. In a nutshell: above 5mph braking is entirely down to the electric motors. The wasteful hydraulic disc brakes play no part except in emergency stops or at speeds below 5mph.

Share this story

194 Reader Comments

Hydrogen I believe is the true future of personal transport for the next 30 - 40 years. Fossil fuels are on the way out, plug-in hybrids and full electric vehicles are a good short-term compromise, but having to recharge batteries breaks the point of owning a single vehicle for general use. Sure, you can commute to your work and back, charging overnight etc, but any unexpected or lengthy trips make it impractical. With hydrogen you simply pull into a fuel station and refill in minutes and continue your journey. It's early days, but we need cars like this hitting the market to encourage the roll out of the hydrogen infrastructure. Once we get over the availability issue, hydrogen will go mainstream and I'll happily make the leap. Now if only there was a hydrogen fuel cell motorcycle in development.....

The travel-to-refuel problem becomes less of an environmental issue when you consider that, even if the hydrogen originates from natural gas, the Rasa will still deliver wheel-to-wheel CO2 emissions in the region of 40g/km.

What is the source on that, from Riversimple?I wonder if the energy required to compress the H2 to 350bar is included as well.

We have a Fiat 500 as an urban car, it is small enough to hustle through the narrow town roads, small enough to park and the fuel economy is really very impressive.

When we bought it we looked at various electric cars and came extremely close to getting a Citroen C0.

The Rasa would probably check enough boxes for us. We occasionally need three seats, but this is occasional enough not to worry us, we have switched from actual shopping in person to getting it delivered and I commute on a motorbike.....

I think this company needs a medal. NONE of the big car manufactures are bringing out anything as imaginative as this. I suppose that is the trait of big business. Takes the small guy to go wild and try somthing new.

I read the monthly lease is £375 + 18p a mile. Not sure how true that is, but seems reasonable considering that's all you even have to pay.

What all this means is that the power sources for cruise and acceleration are decoupled.

This is really smart! I'm glad somebody finally came up with this idea.

I would be the perfect "buyer" for this car, especially with the "can't be bought" approach: I love the car and I love the possibility to lease it instead of buying it.

The problem I see for me is the size: for a car that's not really a car, I would need something even smaller, i.e. shorter, to be able to park it where there's no space for a normal car. A bit like a Smart, that you can park perpendicularly. If I had that, I would stop using my Vespa for commuting (and keep it only for weekends...)

The travel-to-refuel problem becomes less of an environmental issue when you consider that, even if the hydrogen originates from natural gas, the Rasa will still deliver wheel-to-wheel CO2 emissions in the region of 40g/km.

What is the source on that, from Riversimple?I wonder if the energy required to compress the H2 to 350bar is included as well.

Yep, that info was from Riversimple. We've asked them for their methodology though - will let you know when they get back to us.

This is really smart! I'm glad somebody finally came up with this idea.

See Series Hybrid drivetrains. The BMW i3 is just one example of a vehicle that has a low power 'range extender' that just keeps the battery topped up on-the-go. I wonder if this vehicle could actually work the same way? A holdall sized generator is probably about the same size, weight and output as the fuel cell used here.

[quote="What happens once the capacitors are drained? Does that mean I'm stuck with just the fuel cell to accelerate?

It'd be weird to have a car where acceleration drops dramatically if I drive in certain ways.[/quote]

The hydrogen fuel cell can recharge the capacitors directly as shown in the 'network' graphic so theoretically (and as far as I could judge, in practice) the capacitors never run out of juice. It will take a long-term road test of a final production Rasa to fully test this.

[quote="What happens once the capacitors are drained? Does that mean I'm stuck with just the fuel cell to accelerate?

It'd be weird to have a car where acceleration drops dramatically if I drive in certain ways.

The hydrogen fuel cell can recharge the capacitors directly as shown in the 'network' graphic so theoretically (and as far as I could judge, in practice) the capacitors never run out of juice. It will take a long-term road test of a final production Rasa to fully test this.[/quote]

Sure, but the fuel cell only generates 8.5kW. Peak power output is 55kW, which would drain the 1.9MJ capacitors in 34 seconds if I'm doing the maths right.

So if you drain the capacitors, you're limited to accelerating using 1/6th of full power?

For hydrogen to be the fuel of the future two main things need to happen (IMO):

1: fuel cells need to be developed that don't need platinum as a catalyst. In a usual fuel cell car, the price of platinum accounts for 30-50% of the car!!! A fact that was couched as a positive in the article, when it said that 80% of the price of the fuel cell are recyclable ;-). I guess that's one way to see it :lol:

2: the development of chemical solar cells needs to succeed.

Both are being worked on. There has been good success with nickel and copper catalysts and when my reading of the phys.org articles is to be believed then material scientists are working with good success so far on artificial photosynthesis as well.

PS: re: the platinum issue. It's not just its high price, but the fact that the price of platinum is high for a good reason. It's incredibly rare. There is just not enough platinum on this planet to power even all small personal vehicles on the road.

So without platinum free catalysts, the hydrogen economy will simply not happen.

Why do all the hydrogen/electric car manufacturers (except Tesla) love to have those dorky covers on the rear wheels? Any practical reason other than making it uglier?

Because it gives better air flow and hence lower Cd, so its a way to get as much efficiency and hence range as possible. We could do it for gasoline/ diesel vehicles as well, but since they have a surplus of power and range car manufacturers don't seem to feel the need as much, possibly because they'd impact sales more from people finding their car ugly versus those who'd appreciate the extra 1-2 mpg. Much of the issues with car fuel efficiency is driven by what people actually buy when in the showroom, versus what they say they'll buy when asked in the street.

I have two issues on this vehicle (other than the scariness of a high pressure hydrogen container and all that it entails);1) Given the low vehicle weight, I'd want to get clarity on what load that range figure is based on. I'd bet my lunch banana that its based on one passenger <80 kg, not say 2 x 90 kg + 20 kg luggage, and I'd like to know how much of a difference that makes.2) On the same topic, I bet a modern compact 3 cylinder gasoline engine would get down to circa 40 g/km in that light frame and lack of equipment, if tested on same loading basis.

I'd rather drive ten miles than wait the 9.5 hours it takes to fill up a Tesla.

Unless you regularly drive more than 250 miles a day then a Tesla is far more convenient to fill up than a hydrogen car. It might take 9.5 hours to charge up from completely flat but that happens when you are asleep. Arrive home, insert plug. That's it. The next day you magically have a full 'tank' of fuel.

Hydrogen I believe is the true future of personal transport for the next 30 - 40 years. Fossil fuels are on the way out, plug-in hybrids and full electric vehicles are a good short-term compromise

Actually this story made me dream of an electric/hydrogen hybrid. Cut a literal metric ton of battery from a low-end Tesla and replace it with 4 times the fuel-cells of this car, and we might have something that has both the power, the range and only emits vapor.

On the other hand. Hydrogen cars have been right around the corner for almost as long as electric cars, and they don't seem to have a real breakthrough yet.

Hydrogen I believe is the true future of personal transport for the next 30 - 40 years.

Hasn't hydrogen been the fuel of the next 30 years for the last 30 years? Kind of like fusion has been for power generation?

I'm only being partially facetious: in the time that we've made EVs and PHEVs valid, commercial options, hydrogen and fuel-cell cars have never left the pseudo-concept stage and the huge (cost) issues of transport, storage and generation remain pretty much unsolved.

I was talking the other day with a friend of mine who was pointing out that renewable energy is hard to include in a national power grid for a series of reasons (beware, I'm talking about a nuclear-free country, such as Italy): basically, powerplants need power to function, and need a constant supply of power, and all powerplants (which can't just be "turned off" when demand for energy decreases) "waste" power every day dissipating their excess energy production on semi-artificial loads, such as pumping water back in hydroelectric plants at night; solar and wind energy production is inherently unstable, and there is no way today to compensate for the generation swings of renewable energy, as making more solar cells and wind turbines would result in excess production that is very hard to dissipate (that's why you often see immobile wind turbines even in strong wind, I think).

Hydrogen production would happily take the role of artificially loading the power grid, and might also incentivize deployment of renewable energy production systems as an added bonus. (At the moment, it is pointless to deploy more renewable energy production plants because the base capacity is well covered by traditional powerplants). Of course, it would be at a small scale initially, because hydrogen production rates would probably be uncertain, but hydrogen fuel cells - notwithstanding the problem of finding a readily available material for catalysts - could probably bridge the gap between the current situation and technological advancements in battery technology.

I don't see Hydrogen-fueled vehicles shaking up the transportation infrastructure... you substitute the need for gas stations with the need for hydrogen stations, I don't find that elegant or exciting imho.

Electricity you can find almost everywhere nowadays, it's more convenient once you change your fueling habits from the weekly "visits the fueling station" model to a weekly "charge while you sleep" one.

Not to mention how much easier it is to achieve higher energy efficiency from centralizing the energy generation sources, the car magically gets more efficient as the nearby coal plant turns gas or nuclear etc.

Could find a niche in some specific use cases beside daily commute though, so from that angle it's certainly worth the effort to explore.

The travel-to-refuel problem becomes less of an environmental issue when you consider that, even if the hydrogen originates from natural gas, the Rasa will still deliver wheel-to-wheel CO2 emissions in the region of 40g/km.

What is the source on that, from Riversimple?I wonder if the energy required to compress the H2 to 350bar is included as well.

That figure was indeed sourced from Riversimple. This is how they come to that figure:

The derivation of the figure of 40g/km has two parts, the hydrogen consumption, which is approx 200 miles/kg, and the carbon intensity of that hydrogen.

The tolerance on the hydrogen consumption figure I would put at within + or - 10%. This is because a) we have probably not done enough testing to meet Advertising Standards Authority approval and b) the measurement of hydrogen is extraordinarily difficult. In fact, one of the real problems that faces the hydrogen economy is that infrastructure providers can't meter hydrogen accurately enough to meet Trading Standards for the sale of automotive fuels to the public! But I am happy that we are within that band.

The second part of this is the carbon intensity. We have used figures from the reports done by CONCAWE, an oil industry association whose reports are the most widely quoted to justify carbon emissions of alternative fuel cars. In fact, I have just looked at it again and it is done in conjunction with EUCAR and the Joint Research Centre of the EU Commission. This is a 2 volume report - 88 pages of methodology and 14 pages of tabulated data - covering all manner of different fuels and different paths for each of those fuels.

We have used a hydrogen fuel path that we think is most realistic, rather than the one that gives the lowest CO2 figure. This is assuming:- Natural gas, distributed by pipe, 4,000km- Steam reformation of natural gas- Compressed gaseous storage- Distribution by road- No CCS (carbon capture and storage)

On this basis, at 200 miles/kg, we have carbon emissions of 39g/km. If we used the figures for electrolysis using wind-generated electricity, this comes down to 4g/km; the reason it is not zero is because of the embedded carbon in the construction of the wind turbines.

I don't see Hydrogen-fueled vehicles shaking up the transportation infrastructure... you substitute the need for gas stations with the need for hydrogen stations, I don't find that elegant or exciting imho.

Electricity you can find almost everywhere nowadays, it's more convenient once you change your fueling habits from the weekly "visits the fueling station" model to a weekly "charge while you sleep" one.

Not to mention how much easier it is to achieve higher energy efficiency from centralizing the energy generation sources, the car magically gets more efficient as the nearby coal plant turns gas or nuclear etc.

Could find a niche in some specific use cases beside daily commute though, so from that angle it's certainly worth the effort to explore.

Just my 2 cents.

How can you "elegantly" provide charging stations to everyone, when in large parts of the world (Italy included) most of the population lives in apartment blocks and doesn't have a designated parking space?

How can you "elegantly" provide charging stations to everyone, when in large parts of the world (Italy included) most of the population lives in apartment blocks and doesn't have a designated parking space?

I guess that it is all a matter of perspective.

Personally I've never lived in a house or flat or apartment (in the US) that has less than a parking spot. Nearly always I have enjoyed the use of a driveway and/or garage.

Looking at the stats for the UK population

Of the 23.4 million homes (or households) in England and Wales on census day in March 2011, 15 million (64 per cent) were owner occupied and 8.3 million (36 per cent) were rented.

The majority (91 per cent) of owner occupied households lived in a whole house or bungalow, while for those renting, 56 per cent lived in houses while the remaining 44 per cent lived in other accommodation such as flats.

In the UK, 'most' people certainly do not live in apartments, most people live in houses.

It is hard to say what percentage of houses have parking, in my town the answer is that the majority probably do, perhaps 75% or more, also nearly all of the purpose built flats and apartments have designated parking too.

Elegant charging solutions also do not need to be at home, they can be pubic, perhaps in public parking - we have Tesla and Regular chargers in town, or at offices - my office carpark boasts 'over 100 charging stations for example.

For hydrogen to be the fuel of the future two main things need to happen (IMO):

1: fuel cells need to be developed that don't need platinum as a catalyst. In a usual fuel cell car, the price of platinum accounts for 30-50% of the car!!! A fact that was couched as a positive in the article, when it said that 80% of the price of the fuel cell are recyclable ;-). I guess that's one way to see it :lol:

Despite the lol, isn't that a valid point? Yes, there is money tied up in the car, but if it's recoverable that's very significant. Loans with collateral are a lot cheaper than loans without! And that's true whether it's a bank or if you're loaning money to your future self.

I'd rather drive ten miles than wait the 9.5 hours it takes to fill up a Tesla.

Unless you regularly drive more than 250 miles a day then a Tesla is far more convenient to fill up than a hydrogen car. It might take 9.5 hours to charge up from completely flat but that happens when you are asleep. Arrive home, insert plug. That's it. The next day you magically have a full 'tank' of fuel.

Usage cases are obviously highly individual.

Mine is one of regular long distance travel and would mean that if I were to own an electric car, I would also need another car for the three or four trips a month that would be over that range.

The point is, hydrogen fueled cars are 'limited' by the same limitations as petrol fueled cars. There is no usage scenario that they can not fit, in the same manner as petrol fueled cars.

The same is not true of electric cars, which would also require an entirely new nationwide infrastructure costing in the high hundred billion dollar mark if they were ever to be more than niche.

An equivalent nationwide hydrogen infrastructure is estimated to be about 400% cheaper to build, and meets far more needs.

Fuel cell is better than electric... and the second your deity Elon fits one to a Tesla, I'm positive you will suddenly agree.

I can tell you that almost certainly public charging and designated parking wouldn't work in Italy (or at least, they would be hard to implement, also for political reasons). Cities aren't built for them mostly (most cities and towns have significant historical areas), and this is true in lots of (high income!) Mediterranean countries in general. Anyway I don't see why we shouldn't have competing technologies. We already have a variety of fuels, for example diesel, petrol, CNG and LPG. In Brazil they also use ethanol. I can see lots of advantages in fuel cells and I don't see why we should move towards one and only one solution for electric cars. If anything, I suppose that a lot of technology can or would be shared between battery-operated and fuel cell electric cars.

This is really smart! I'm glad somebody finally came up with this idea.

See Series Hybrid drivetrains. The BMW i3 is just one example of a vehicle that has a low power 'range extender' that just keeps the battery topped up on-the-go. I wonder if this vehicle could actually work the same way? A holdall sized generator is probably about the same size, weight and output as the fuel cell used here.

I have owned one of the first North american versions of the BMW i3 with the range extender option.

For the size of the vehicle; consider each and every option that similar sized gasoline vehicles have. One of the more important stats; how much it costs to fill up the vehicle and/or the cost per gallon. Even for similar sized fairly fuel efficient vehicles such as a Kia Soul (one of many, many such examples) the cost to fill it up is about $25.oo. For that cost one can travel about three hundred miles.

It cost me $1.90 to travel that same 300 miles in the i3.

Two added bonuses... Got the full $7,5oo tax credit back, thereby making the i3 an incredibly great deal financially. Already had full solar/battery throughout my residence. So actually that $1.90 per three hundred miles does not at all apply to me - the cost is zero. About the only thing I'll pay for in maintenance is tires, brakes, etc...

300 miles on 1.5kg is impressive energy density by mass. Assuming a gallon of standard gasoline is about 2.5kg which in my minivan I get 26 mpg freeway. Not an apples-to-apples comparison as a minivan designed for people moving efficiency is less energy efficient than a small commuter vehicle designed for energy efficiency, but the 10-fold energy density is impressive.

I'd rather drive ten miles than wait the 9.5 hours it takes to fill up a Tesla.

Just how does the general public attach a device that supplies 350 bar of H2? And how many of these are available? If it sends the gas at a lower pressure, does it take long to compress it to 350 bar?

The answer presently lies in Europe. Depending upon where one travels in Europe, some countries have stations that generate their own hydrogen on site - no deliveries ever needed. Compression is quite easy to both achieve and maintain.